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C1.6 - Plant Oils & their uses
Transcript of C1.6 - Plant Oils & their uses
Where can we find plant oils?
Extracting vegetable oil
What grade am I?
Plant oils and their uses
Saturated vs. Unsaturated
Saturated fats contain no carbon-to-carbon double bonds. The straight fatty acids chains pack closely together.
Unsaturated fats contain at least one carbon-to-carbon double bond. This bends the fatty acid chains and they cannot pack closely together.
Saturated fats are less healthy than unsaturated fats because the dense packing makes them harder for the body to digest.
Saturated fats become deposited in the blood vessels, leading to high blood pressure, possibly causing strokes and heart attacks.
Look at the results below
Which oil contains more double bonds?
Sunflower vs. Olive oil
Saturated and unsaturated oils and fats
Know the difference between saturated and unsaturated fats.
Be able to show saturation/ unsaturation using bromine
Be able to write an equation for the addition of bromine to a double bond.
Saturated and unsaturated fats
How is margarine made?
Plant Oils & their Uses
What is hydrogenation?
Pressing & Filtration
What is an emulsion?
Using Vegetable oils
Oils in Food and Fuel
Distillation and chemical processes can also be used to make plant oils.
Oils obtained in this way are often labelled “refined”.
Plant oils are types of fat and can provide the body with energy. They are also good sources of vitamins.
Oils can be made by crushing the seeds, beans and nuts of some plants, including olives and sunflowers.
First the plant material is crushed to make a paste.
The paste is then pressed to remove water and other impurities.
Oils obtained in this way are often labelled “virgin” or “cold pressed”.
What could be used to prevent the ingredients separating?
Adding oil to water in a particular way forms an emulsion.
Salad dressings often have to be shaken before use because the ingredients have separated.
Fine droplets of oil become dispersed through out the water, This give the emulsion a thick and creamy texture.
Milk, salad dressings and paint are all examples of emulsions.
Oils and water are insoluble in each other and do not naturally mix. These liquids are immiscible.
Natural and artificial emulsifiers are used to stop oil and water separating into layers.
This is achieved by keeping the oil / water droplets separate, maintaining an emulsion.
Mayonnaise is made using egg yolk.
This contain lecithin, which is a natural emulsifier.
Mayonnaise is an emulsion.
Unlike salad dressings it does not separate when it is left to stand.
Why is this?
Emulsifiers have a hydrophilic (‘water loving’) part and a hydrophobic (‘water hating’) part.
What stops emulsions from separating?
Not all the carbon-to-carbon double bonds are broken. This means that margarines still contain unsaturated fats. The oil is partially hydrogenated.
Nickel is used as a catalyst for this reaction. It is filtered out before the margarine is packaged and sold.
Most modern margarines are made from plant oils. The oil is heated and hydrogen is pumped through it. This is called hydrogenation.
Margarine was originally made using buttermilk, a waste product from making butter.
Some of the carbon-to-carbon double bonds in the plant oils are broken and extra hydrogen atoms are added. This hardens the oil to make it a solid at room temperature.
Medical organisations in the UK have campaigned to get trans fats clearly labelled on food. Some supermarkets are now removing trans fats from their own-brand foods.
Trans fats are a type of fat that the body
finds difficult to break down. These molecules can block the arteries of the heart.
However, partially hydrogenated plant oils are commonly used in food products, such as biscuits and ready meals.
Partially hydrogenated oils were used to make margarine. Today, most margarines are made using other methods and contain less trans fat.
Trans fats can be formed by the partial hydrogenation of plant oils.
What are trans fats?
However, most people eat fewer foods containing omega-3.
It is easy to get enough omega-6 because corn and soya oil are often added to processed food.
– found in corn, sunflower and soya oil
– found in flax seeds (linseed), pumpkin seeds, walnuts and oily fish
There are two main types of EFAs:
Essential fatty acids (EFAs) can be found in plant oils. They are needed by the body but it cannot produce them.
What are essential fatty acids?
Some research has shown that EFAs can help lower blood pressure and decrease the risk of blood clots.
Plant oils activity
How an emulsion is made.
Making an emulsion
An emulsion is made by combining oil based and water-based ingredients.
An emulsion has a thick creamy texture.
Oil and water do not naturally mix.
They can be made to mix in an emulsion.
One method is to add oil to water very slowly. The mixture is stirred continuously
Stirring the mixture causes small droplets of oil to be dispersed throughout the water.
This forms a thick creamy emulsion.
Emulsions can also be made by adding water to oil. The water droplets are suspended in the oil.
Magnifying the emulsion shows droplets of oil are held in suspension in the water.
When the emulsion is left to stand, the water and oil separate slowly over time.
Why do we have to shake salad dressings and other emulsions before use?
Note: this process uses a Nickel catalyst to add the hydrogen to the double bond
Making oils into fats
Because they don’t fit well together, the size of the forces between unsaturated fats decreases. This results in lower melting points, hence, unsaturated fats tend to be oils.
‘Flexi-Fuel’ vehicles, fitted with modified fuel injection systems, can run on E85 fuel (85% bioethanol, 15% petrol), which cuts carbon dioxide emissions by 70% compared to normal petrol-engine cars.
Bioethanol is an alcohol produced by the natural fermentation of the carbohydrates (such as starch) in sugar beet/cane or wheat crops.
What is bioethanol?
Biodiesel can be mixed with conventional diesel, which significantly reduces emissions, especially toxic hydrocarbons, particulates and carbon monoxide.
There are few garages in the UK that sell biodiesel. Home-made fuels, usually from waste vegetable oils, are heavily taxed.
Biodiesel is produced by chemically reacting vegetable oils or animal fats with alcohol and a catalyst. The process can be completed in 12 hours.
What is biodiesel?
By-products of production, such as pressed seedcake, can be burnt in power stations instead of fossil fuels or used as an animal feed
Advantages of biofuels
What are some of the advantages of using biofuels?
Storage, transport and distribution costs are low as biofuels can be handled in the same way as conventional fuels.
Biofuels are carbon neutral: the carbon released during combustion comes from the carbon dioxide the plants took in when they were growing.
The high demand for land to plant biofuel crops can lead to deforestation and habitat loss, for example in Malaysia.
What are some of the disadvantages of using biofuels?
There are few UK producers of biofuels, and only small quantities of fuel are made. Biofuels therefore need to be imported, mainly from Brazil and South-East Asia.
Although biofuels themselves produce relatively little when combusted, their production needs energy from fossil fuels.
Disadvantages of biofuels
Although fossil fuels are convenient sources of energy, they are very polluting, and will one day run out.
As a result, some people have already begun using alternative fuels to power their vehicles, such as biofuels .
Why is it important to develop and use these fuels before oil supplies run out?
Most vehicles in the world use petrol or diesel as a fuel. These are produced from crude oil, a fossil fuel.
The need for alternative fuels
Lots of land is required to grow the sugar beet/cane or wheat crops. This uses up land; either land used for growing food crops, or deforested land (forests cleared to be able to grow crops).
Biodiesel in the UK
Testing for double-bonds
We already know the main difference between the
of saturated, monounsaturated and polyunsaturated oils.
But how do we tell the difference between them
Put these plant oils in order of unsaturation, starting with the most unsaturated.
type of fat formed during hydrogenation
no carbon-carbon double bonds
chemical used to test for unsaturation
essential fatty acid found in soya oil
two or more carbon-carbon double bonds
essential fatty acid found in walnuts
process used to make margarine
one carbon-carbon-double bond
Unsaturated fats are and have low melting points due to weak forces of attraction between molecules, because of their bent in shape.
By adding hydrogen gas (at 60 C, using a Nickel catalyst) we break the carbon-carbon double bond making it saturated and straighter.
As a result, molecules are more closely packed, with stronger forces of attraction between them, leading to higher melting points.